Core formula
Daily AC Cost = AC Power in kW x Hours Used x Electricity Rate per kWh.
Monthly AC Cost = Daily AC Cost x Days Used.
Power and efficiency assumptions
When a user enters actual wattage, that value gives the most direct estimate. When wattage is not available, AC Bill Pro estimates power from cooling capacity and efficiency ratings such as SEER or EER. Higher efficiency ratings generally reduce estimated electricity use for the same cooling load.
Electricity rate assumptions
Electricity cost depends heavily on the utility rate. The calculator works best when users enter the rate from their own bill. State or country examples should be treated as planning estimates because taxes, fixed utility charges, time-of-use pricing, and seasonal charges vary by provider.
Runtime assumptions
Runtime is usually the biggest driver of AC bills. A home in a hot climate, a poorly insulated home, or a lower thermostat setting can increase runtime even when the equipment size stays the same.
Limitations
AC Bill Pro is an educational estimate, not a utility bill guarantee. Actual bills can change because of humidity, duct leakage, maintenance condition, thermostat behavior, occupancy, sun exposure, insulation, utility fees, and non-AC electricity use.
Reference sources
For background checks and editorial review, compare assumptions with public resources from the U.S. Energy Information Administration, U.S. Department of Energy, and ENERGY STAR central air conditioner guidance.